Re: [Boost-users] [Container] --begin() on empty deque crashes

On Jan 19, 2013, at 8:23 PM, TONGARI wrote:

2013/1/20 Ion Gaztañaga El 19/01/2013 13:06, TONGARI escribió:

Hi there,

The code below would simply crash on g++ 4.7.1/MinGW with default optimization level, it doesn't shown with -O/1/2/3 ---------------------------------------- boost::container::deque<int> d; --d.begin(); ----------------------------------------

The problem is that decrementing a begin iterator is not a valid operator, since it would point out of the container.

But wouldn't it be a valid operation as long as we don't dereference from it?

I don't believe so. If it was a pointer, then yes. The closest I could find in the standard was section 24.2.6 (talking about bidirectional iterators), it says that a precondition for --r is: there exists s such that r == ++s -- Marshall Marshall Clow Idio Software mailto:mclow.lists@gmail.com A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait). -- Yu Suzuki